Wednesday, May 14, 2008

Suspect Soundings - Two Recent Examples

The figures below show soundings from Flagstaff AZ yesterday morning at 1200 UTC and from Ft. Worth TX this morning at 1200 UTC. Both have suspect layers, but the cause of the problems are not obvious.

Figure 1 - KFGZ

This sounding indicates a very dry layer of almost 100 mb vertical extent just above 700 mb. It had been raining for several hours and at the time of release Flagstaff was reporting moderate to heavy snowfall. The snow continued for several hours after sounding time. The dry layer certainly does not seem physically realistic, given the steady precipitation event that was underway.

Figure 2 - KFWD

This morning's sounding at FWD indicates a strongly super-adiabatic lapse at about 710 mb. This excursion causes a layer that appears to be several degrees too cool from about 710 to 550 mb. The net result is that sounding analysis software routines would produce CAPE values that were likely too great. Since the sonde did not, apparently, rise into a very dry layer, the reason for the super-adiabatic layer aloft is not clear.

Both of these soundings may illustrate random instabilities within these two RSS sonde's internal electronics, but this is just a guess on my part.

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